1. Field of the Invention
The invention relates to an automated glass and plastic refuse sorter, and, more particularly, to an automated sorter for use in sorting post-consumer glass and plastic containers and refuse by color.
Landfills, into which waste material is deposited, are a limited resource. The material placed into landfills contains large amounts of recyclable materials, including glass and plastic refuse such as post-consumer glass and plastic containers. Recovery of these materials can extend the life of landfills.
Materials Recovery Facilities (MRF) provide for the collection, sorting and marketing of discarded recyclable materials. For MRF to be cost effective, it must recover high percentages of recyclable materials and prepare them into a marketable condition. Simply collecting recyclable materials is only part of the recycling effort.
A critical part of the recycling process is the preparation of the materials into a marketable condition. Due to special requirements for market use, glass and plastic refuse is particularly prone to non-marketability problems. In order for glass refuse to be marketable to glass container manufacturers, it must be relatively free of contaminants and sorted by color. In order for plastic refuse to be marketable at its highest value, it must be separated by both color and by polymer group.
2. Discussion of the Related Art
The color sorting of whole post-consumer containers is presently accomplished by hand-sorting, either by the consumer prior to collection, or at the MRF after collection. Consumer sorting is undesirable, as it has high costs incurred by the separate collection and transportation, and moreover, it very likely does not maximize the overall amount recovered. A special problem presented by glass is that it may be broken in collection, transportation or processing. Such glass cannot be hand sorted due to excessive labor requirements and obvious safety risks. Thus, broken glass primarily remains unsorted, and hence is not recycled due to low marketability of mixed color glass.
A variety of conventional sorting apparatuses are known, including glass sorting apparatuses. For example, U.S. Pat. No. 3,650,396, to Gillespie et al., discloses an apparatus for sorting refuse into its components for recycle. A glass sorting section feeds glass particles one by one through a housing, where the particles are sorted into clear and colored particles. One disadvantage with such a singulation conventional sorting apparatus is that the particles must be fed in one by one. Another disadvantage is that the particles can not be extremely disparate in size.
Another singulation particle sorter is disclosed in U.S. Pat. No. 4,252,240, to Satake. A shooter feeds pieces one at a time, and an air ejector is actuated by a photosensitive detector to discriminate unacceptable particles. U.S. Pat. No. 4,513,868, to Culling, et al., discloses yet another singulation sorter. It also discloses a photoelectric means for comparing the average transmission or emission of light by a background behind the objects. Other traditional singulation sorting machines are disclosed in U.S. Pat. Nos. 4,630,736, and 4,699,273.
Traditional devices and methods for sorting glass by color are known. For example, U.S. Pat. No. 4,077,871, to Kumar et al., discloses a process for color sorting of particulate glass by raising the temperature of the glass and contacting the differentially heated glass with an organic thermoplastic material which melts in a narrow temperature range. The glass particles can then be sorted by various means, including froth flotation or adhesion. U.S. Pat. No. 4,076,979, to Walter et al., discloses a bottle color identification apparatus, which can be used to sort returnable bottles with the same size and shape into their respective colors.
Other traditional sorters are known for use with other objects. For example, U.S. Pat. No. 3,782,544, to Perkins, III, discloses a singulation sorter for sorting tobacco leaves according to color and brightness by comparison to a background color. U.S. Pat. No. 4,909,930, to Cole, discloses a sorter for separating foreign objects from a stream of material. Overlapping detection zones are utilized to actuate one or a group of nozzles to reject, for example, a piece of paper. Unfortunately, these traditional sorters are not useful for sorting discarded post-consumer bottles and cullet.